Beta to gamma phase cycleable electrochemically active nickel hydroxide material

ABSTRACT

An nickel hydroxide positive electrode active material which can be made by an ultrasonic precipitation method. The nickel hydroxide active material is characterized by the ability to reversibly cycle between the beta and gamma nickel hydroxide crystalline phases during electrochemical charge and discharge. The material may also be characterized by a high degree of local ordering of the hydroxyl ions.

CONTINUING APPLICATION INFORMATION

The instant application is a continuation-in-part of U.S. patentapplication Ser. No. 08/496,491, filed Jun. 26, 1995 and now abandoned,by Stanford R. Ovshinsky and Rosa Young, and entitled "ULTRASONIC METHODFOR FORMING SPHERICAL NICKEL HYDROXIDE".

FIELD OF THE INVENTION

The present invention relates to an electrochemically active nickelhydroxide materials for use in rechargeable battery positive electrodes.More specifically, the instant invention relates to a spherical nickelhydroxide particulate which electrochemically cycles between the betaand gamma phases. The material has unique properties not found in othernickel hydroxide materials and may be produced by an ultrasonic method.

BACKGROUND OF THE INVENTION

In rechargeable alkaline cells, weight and portability are importantconsiderations. It is also advantageous for rechargeable alkaline cellsto have long operating lives without the necessity of periodicmaintenance. Rechargeable alkaline cells are used in numerous consumerdevices such as calculators, portable radios, and cellular phones. Theyare often configured into a sealed power pack that is designed as anintegral part of a specific device. Rechargeable alkaline cells can alsobe configured as larger cells that can be used, for example, inindustrial, aerospace, and electric vehicle applications.

There are many known types of Ni based cells such as nickel cadmium("NiCd"), nickel metal hydride ("Ni--MH"), nickel hydrogen, nickel zinc,and nickel iron cells. NiCd rechargeable alkaline cells are the mostwidely used although it appears that they will be replaced by Ni--MHcells. Compared to NiCd cells, Ni--MH cells made of syntheticallyengineered materials have superior performance parameters and contain notoxic elements.

Stanford R. Ovshinsky, by applying his fundamental principles ofdisorder, pioneered the development of the first commercial nickel metalhydride (NiMH) battery. For more than three decades, virtually everyother manufacturer in the world studied the NiMH battery technology, butno commercial battery of this kind existed until after the publicationof U.S. Pat. No. 4,623,597 to Ovshinsky and Ovshinsky's relatedtechnical papers which disclosed basic and fundamentally new principlesof battery material design. NiMH batteries are the only truly "green"battery because they can be completely recycled. NiMH batteries are theonly rechargeable battery that can meet society's requirements for anecological, renewable source of electrochemical energy.

As previously mentioned, Stanford R. Ovshinsky was responsible forinventing new and fundamentally different electrochemical electrodematerials. As predicted by Ovshinsky, detailed investigation byOvshinsky's team determined that reliance on simple, relatively purecompounds was a major shortcoming of the prior art. Relatively purecrystalline compounds were found to have a low density of hydrogenstorage sites, and the type of sites available occurred accidently andwere not designed into the bulk of the material. Thus, the efficiency ofthe storage of hydrogen and the subsequent release of hydrogen to formwater was determined to be poor. By applying his fundamental principlesof disorder to electrochemical hydrogen storage, Ovshinsky drasticallydeparted from conventional scientific thinking and created a disorderedmaterial having an ordered local environment where the entire bulk ofthe material was provided with catalytically active hydrogen storagesites.

Short-range, or local, order is elaborated on in U.S. Pat. No. 4,520,039to Ovshinsky, entitled Compositionally Varied Materials and Method forSynthesizing the Materials, the contents of which are incorporated byreference. This patent discusses how disordered materials do not requireany periodic local order and how, by using Ovshinsky's techniques,spatial and orientational placement of similar or dissimilar atoms orgroups of atoms is possible with such increased precision and control ofthe local configurations that it is possible to produce qualitativelynew phenomena. In addition, this patent discusses that the atoms usedneed not be restricted to "d band" or "f band" atoms, but can be anyatom in which the controlled aspects of the interaction with the localenvironment and/or orbital overlap plays a significant role physically,electronically, or chemically so as to affect physical properties andhence the functions of the materials. Ovshinsky's use of disorderedmaterials has fundamental scientific advantages. The elements of thesematerials offer a variety of bonding possibilities due to themultidirectionality of d-orbitals. The multidirectionality ("porcupineeffect") of d-orbitals provides for a tremendous increase in density andhence active storage sites. These techniques result in means ofsynthesizing new materials which are disordered in several differentsenses simultaneously.

Ovshinsky had previously found that the number of surface sites could besignificantly increased by making an amorphous film that resembled thesurface of the desired relatively pure materials. As Ovshinsky explainedin Principles and Applications of Amorphicity, Structural Change, andOptical Information Encoding, 42 Journal De Physique at C4-1096 (October1981):

Amorphicity is a generic term referring to lack of X-ray diffractionevidence of long-range periodicity and is not a sufficient descriptionof a material. To understand amorphous materials, there are severalimportant factors to be considered: the type of chemical bonding, thenumber of bonds generated by the local order, that is its coordination,and the influence of the entire local environment, both chemical andgeometrical, upon the resulting varied configurations. Amorphicity isnot determined by random packing of atoms viewed as hard spheres nor isthe amorphous solid merely a host with atoms imbedded at random.Amorphous materials should be viewed as being composed of an interactivematrix whose electronic configurations are generated by free energyforces and they can be specifically defined by the chemical nature andcoordination of the constituent atoms. Utilizing multi-orbital elementsand various preparation techniques, one can outwit the normalrelaxations that reflect equilibrium conditions and, due to thethree-dimensional freedom of the amorphous state, make entirely newtypes of amorphous materials--chemically modified materials . . .

Once amorphicity was understood as a means of introducing surface sitesin a film, it was possible to produce "disorder" that takes into accountthe entire spectrum of local order effects such as porosity, topology,crystallites, characteristics of sites, and distances between sites.Thus, rather than searching for material modifications that would yieldordered materials having a maximum number of accidently occurringsurface irregularities, Ovshinsky's team at ECD began constructing"disordered" materials where the desired irregularities were tailormade. See, U.S. Pat. No. 4,623,597, the disclosure of which isincorporated by reference.

The term "disordered," as used herein corresponds to the meaning of theterm as used in the literature, such as the following:

A disordered semiconductor can exist in several structural states. Thisstructural factor constitutes a new variable with which the physicalproperties of the material! . . . can be controlled. Furthermore,structural disorder opens up the possibility to prepare in a metastablestate new compositions and mixtures that far exceed the limits ofthermodynamic equilibrium. Hence, we note the following as a furtherdistinguishing feature. In many disordered materials! . . . it ispossible to control the short-range order parameter and thereby achievedrastic changes in the physical properties of these materials, includingforcing new coordination numbers for elements . . .

S. R. Ovshinsky, The Shape of Disorder, 32 Journal of Non-CrystallineSolids at 22 (1979) (emphasis added).

The "short-range order" of these disordered materials are furtherexplained by Ovshinsky in The Chemical Basis of Amorphicity: Structureand Function, 26:8-9 Rev. Roum. Phys. at 893-903 (1981):

S!hort-range order is not conserved . . . Indeed, when crystallinesymmetry is destroyed, it becomes impossible to retain the sameshort-range order. The reason for this is that the short-range order iscontrolled by the force fields of the electron orbitals therefore theenvironment must be fundamentally different in corresponding crystallineand amorphous solids. In other words, it is the interaction of the localchemical bonds with their surrounding environment which determines theelectrical, chemical, and physical properties of the material, and thesecan never be the same in amorphous materials as they are in crystallinematerials . . . The orbital relationships that can exist inthree-dimensional space in amorphous but not crystalline materials arethe basis for new geometries, many of which are inherentlyanti-crystalline in nature. Distortion of bonds and displacement ofatoms can be an adequate reason to cause amorphicity in single componentmaterials. But to sufficiently understand the amorphicity, one mustunderstand the three-dimensional relationships inherent in the amorphousstate, for it is they which generate internal topology incompatible withthe translational symmetry of the crystalline lattice . . . What isimportant in the amorphous state is the fact that one can make aninfinity of materials that do not have any crystalline counterparts, andthat even the ones that do are similar primarily in chemicalcomposition. The spatial and energetic relationships of these atoms canbe entirely different in the amorphous and crystalline forms, eventhough their chemical elements can be the same . . .

Short-range, or local, order is elaborated on in U.S. Pat. No. 4,520,039to Ovshinsky, entitled Compositionally Varied Materials and Method forSynthesizing the Materials, the contents of which are incorporated byreference. This patent discusses how disordered materials do not requireany periodic local order and how, by using Ovshinsky's techniques,spatial and orientational placement of similar or dissimilar atoms orgroups of atoms is possible with such increased precision and control ofthe local configurations that it is possible to produce qualitativelynew phenomena. In addition, this patent discusses that the atoms usedneed not be restricted to "d band" or "f band" atoms, but can be anyatom in which the controlled aspects of the interaction with the localenvironment plays a significant role physically, electrically, orchemically so as to affect the physical properties and hence thefunctions of the materials. These techniques result in means ofsynthesizing new materials which are disordered in several differentsenses simultaneously.

By forming metal hydride alloys from such disordered materials,Ovshinsky and his team were able to greatly increase the reversiblehydrogen storage characteristics required for efficient and economicalbattery applications, and produce, for the first time, commerciallyviable batteries having high density energy storage, efficientreversibility, high electrical efficiency, bulk hydrogen storage withoutstructural change or poisoning, long cycle life, and deep dischargecapability.

The improved characteristics of these alloys result from tailoring thelocal chemical order and hence the local structural order by theincorporation of selected modifier elements into a host matrix.Disordered metal hydride alloys have a substantially increased densityof catalytically active sites and storage sites compared to conventionalordered materials. These additional sites are responsible for improvedefficiency of electrochemical charging/discharging and an increase inelectrical energy storage capacity. The nature and number of storagesites can even be designed independently of the catalytically activesites. More specifically, these disordered multi-component alloys arethermodynamically tailored to allow storage of hydrogen atoms at a widerange of modulated bonding strengths within the range of reversibilitysuitable for use in secondary battery applications.

Based on these principles of disordered materials, described above, afamily of extremely efficient electrochemical hydrogen storage materialswere formulated. These are the Ti--V--Zr--Ni type active materials suchas disclosed by Ovshinsky's team in U.S. Pat. No. 4,551,400 ("the '400Patent"), the disclosure of which is incorporated by reference. Thesematerials reversibly form hydrides in order to store hydrogen. All thematerials used in the '400 Patent utilize a T--V--Ni composition, whereat least Ti, V, and Ni are present with at least one or more of Cr, Zr,and Al. The materials of the '400 Patent are generally multiphasepolycrystalline materials, which may contain, but are not limited to,one or more phases of Ti--V--Zr--Ni material with C₁₄ and C₁₅ typecrystal structures. Other Ti--V--Zr--Ni alloys may also be used forfabricating rechargeable hydrogen storage negative electrodes. One suchfamily of materials are those described in U.S. Pat. No. 4,728,586 ("the'586 Patent"), titled Enhanced Charge Retention Electrochemical HydrogenStorage Alloys and an Enhanced Charge Retention Electrochemical Cell,the disclosure of which is incorporated by reference.

The characteristic surface roughness of the metal electrolyte interfaceis a result of the disordered nature of the material. Since all of theconstituent elements, as well as many alloys and phases of them, arepresent throughout the metal, they are also represented at the surfacesand at cracks which form in the metal/electrolyte interface. Thus, thecharacteristic surface roughness is descriptive of the interaction ofthe physical and chemical properties of the host metals as well as ofthe alloys and crystallographic phases of the alloys, in an alkalineenvironment. The microscopic chemical, physical, and crystallographicparameters of the individual phases within the hydrogen storage alloymaterial are believed to be important in determining its macroscopicelectrochemical characteristics.

In addition to the physical nature of its roughened surface, it has beenobserved that V--Ti--Zr--Ni alloys tend to reach a steady state surfacecondition and particle size. This steady state surface condition ischaracterized by a relatively high concentration of metallic nickel.These observations are consistent with a relatively high rate of removalthrough precipitation of the oxides of titanium and zirconium from thesurface and a much lower rate of nickel solubilization. The resultantsurface seems to have a higher concentration of nickel than would beexpected from the bulk composition of the negative hydrogen storageelectrode. Nickel in the metallic state is electrically conductive andcatalytic, imparting these properties to the surface. As a result, thesurface of the negative hydrogen storage electrode is more catalytic andconductive than if the surface contained a higher concentration ofinsulating oxides.

The surface of the negative electrode, which has a conductive andcatalytic component--the metallic nickel--appears to interact withchromium alloys in catalyzing various hydride and dehydride reactionsteps. To a large extent, many electrode processes, including competingelectrode processes, are controlled by the presence of chromium in thehydrogen storage alloy material, as disclosed in the '586 Patent.

Because of the increased performance realized by following the teachingsof Ovshinsky, the performance of the negative electrodes have increasedramatically in the most recent decade, this in turn has caused thepositive nickel hydroxide electrodes to lag behind in performancecharacteristics and, as a result, to cause a bottleneck in theproduction of extremely high performance batteries. To this end,Ovshinsky and his colleagues have now turned their focus to the nickelhydroxide electrodes, applying Ovshinsky's fundamentals of disorder toan area which it has never before been applied.

Ni--MH cells utilize a negative electrode that is capable of thereversible electrochemical storage of hydrogen. Ni--MH cells usuallyemploy a positive electrode of nickel hydroxide material. The negativeand positive electrodes are spaced apart in the alkaline electrolyte.Upon application of an electrical potential across a Ni--MH cell, theNi--MH material of the negative electrode is charged by theelectrochemical absorption of hydrogen and the electrochemical dischargeof a hydroxyl ion, as shown in equation (1): ##STR1## The negativeelectrode reactions are reversible. Upon discharge, the stored hydrogenis released to form a water molecule and release an electron. Thereactions that take place at the nickel hydroxide positive electrode ofa Ni--MH cell are shown in equation (2): ##STR2## Ni--MH materials arediscussed in detail in U.S. Pat. No. 5,277,999 to Ovshinsky, et al., thecontents of which are incorporated by reference.

In alkaline rechargeable cells, the discharge capacity of a nickel basedpositive electrode is limited by the amount of active material, and thecharging efficiencies. The charge capacities of a Cd negative electrodeand a MH negative electrode are both provided in excess, to maintain theoptimum capacity and provide overcharge protection. Thus, a goal inmaking the nickel positive electrode is to obtain as high an energydensity as possible. The volume of a nickel hydroxide positive electrodeis sometimes more important than weight. The volumetric capacity densityis usually measured in mAh/cc and specific capacity is written as mAh/g.

At present, sintered or pasted nickel hydroxide positive electrodes areused in NiCd and Ni--MH cells. The process of making sintered electrodesis well known in the art. Conventional sintered electrodes normally havean energy density of around 480-500 mAh/cc. In order to achievesignificantly higher loading, the current trend has been away fromsintered positive electrodes and toward foamed and pasted electrodes.

Sintered nickel electrodes have been the dominant nickel electrodetechnology for several decades for most applications. These consist of aporous nickel plaque of sintered high surface area nickel particlesimpregnated with nickel hydroxide active material either by chemical orelectrochemical methods. While expensive, sintered electrodes providehigh power, high reliability, and high cycle life, but not the highestenergy density. They are likely to remain important for high reliabilitymilitary and aerospace applications for some time.

Pasted nickel electrodes consist of nickel hydroxide particles incontact with a conductive network or substrate, preferably having a highsurface area. There have been several variants of these electrodesincluding the so-called plastic-bonded nickel electrodes which utilizegraphite as a microconductor and also including the so-called foam-metalelectrodes which utilize high porosity nickel foam as a substrate loadedwith spherical nickel hydroxide particles and cobalt conductivityenhancing additives. Pasted electrodes of the foam-metal type havestarted to penetrate the consumer market due to their low cost andhigher energy density relative to sintered nickel electrodes.

Conventionally, the nickel battery electrode reaction has beenconsidered to be a one electron process involving oxidation of divalentnickel hydroxide to trivalent nickel oxyhydroxide on charge andsubsequent discharge of trivalent nickel oxyhydroxide to divalent nickelhydroxide, as shown in equation 2 hereinbelow.

Some recent evidence suggests that quadrivalent nickel is involved inthe nickel hydroxide redox reaction. This is not a new concept. In fact,the existence of quadrivalent nickel was first proposed by Thomas Edisonin some of his early battery patents. However, full utilization ofquadrivalent nickel has never been investigated.

In practice, electrode capacity beyond the one-electron transfertheoretical capacity is not usually observed. One reason for this isincomplete utilization of the active material due to electronicisolation of oxidized material. Because reduced nickel hydroxidematerial has a high electronic resistance, the reduction of nickelhydroxide adjacent the current collector forms a less conductive surfacethat interferes with the subsequent reduction of oxidized activematerial that is farther away.

Ovshinsky and his team have developed positive electrode materials thathave demonstrated reliable transfer of more than one electron per nickelatom. Such materials are described in U.S. Pat. Nos. 5,344,728 and5,348,822 (which describe stabilized disordered positive electrodematerials) and copending U.S. patent application Ser. No. 08/300,610filed Aug. 23, 1994, and U.S. patent application Ser. No. 08/308,764filed Sep. 19, 1994.

While Ovonic Battery Company's advances in the positive electrode nickelhydroxide materials have been useful in increasing the capacity of theraw nickel hydroxide materials, production of spherical powders forincorporation into pasted electrodes has heretofore be accomplished by aspray drying technique. It is essential to produce the nickel hydroxideactive materials in spherical powder form so that their packing densityis high when used in the pasted electrodes. Therefore, since the spraydrying process is highly energy intensive, complicated and thereforecostly, a simple, economical method for producing spherical nickelhydroxide powder is desirable.

SUMMARY OF THE INVENTION

The instant invention includes an improved nickel hydroxide positiveelectrode active material which can be made by an ultrasonicprecipitation method. The nickel hydroxide active material ischaracterized by the ability to reversibly cycle between the beta andgamma nickel hydroxide crystalline phases during electrochemical chargeand discharge. The material may also be characterized by a high degreeof local ordering of the hydroxyl ions.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows an electron microscope image of spherical nickel hydroxideof the instant invention at a magnification of 2000×;

FIG. 2 shows an x-ray plot for nickel hydroxide of the instant inventionin the discharged state showing the predominant beta phase peak at thepoint indicated as 4.63337;

FIG. 3 shows an x-ray plot for nickel hydroxide of the instant inventionin the charged state showing the predominant gamma phase peak at thepoint indicated as 7.09673;

FIG. 4 is a plot of the infrared spectra of three different nickelhydroxide materials showing the wavenumber region containing the O--Hstretching band which extends from ˜3700 cm⁻¹ to 2500 cm⁻¹, specificallytrace (A) is of a nickel hydroxide produced by non-ultrasonicprecipitation, trace (B) is of a nickel hydroxide material of theinstant invention, while trace (C) is the spectrum of a typicalbeta-Ni(OH)₂ supplied by Tanaka K.K.; and

FIG. 5 is a plot of "C" cell capacity versus cycle number for a batteryutilizing the nickel hydroxide material of the instant invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is a nickel hydroxide active material which ischaracterized by the ability to reversibly cycle between the beta andgamma nickel hydroxide crystalline phases during electrochemical chargeand discharge. The material may be produced by ultrasonic precipitationfrom liquid ionic precursors. Additionally, the formed nickel hydroxideparticulate is spherical and is therefore very useful as a positiveelectrode material in pasted nickel hydroxide battery electrodes, as itsspherical shape provides for a good packing density.

EXAMPLE

A metal nitrate solution containing nickel, cobalt and calcium metalions was produced. The metal nitrate solution was a 1 molar solutioncontaining 90 mole % Ni(NO₃)₂, 6 mole % Ca(NO₃)₂ and 4 mole % Co(NO₃)₂.One liter of this metal nitrate solution was used as the starting liquidfor a precipitation reaction into which 0.990 liters of a 2 molarammonium hydroxide solution was added at a rate. During precipitation,the metal nitrate solution into which the ammonium hydroxide is beingadded is subjected to ultrasonic energy from an ultrasonic bath.

After the precipitation was finished, the precipitate was filtered toremove the mother liquor. The filtrate was then washed byre-slurrying/re-filtering with 2 liters of de-ionized water, 2 liters of1 molar NaOH, and four more separate additions of 2 liters of de-ionizedwater, sequentially.

The resultant washed/filtered nickel hydroxide cake was then air driedin an oven to remove the excess water, after which the dried cake wasground and sieved. The resultant powder, shown in FIG. 1, was sphericalnickel hydroxide particulate of a relatively uniform 3-8 microns insize.

Microstructural Changes

In addition to the formation of spherical nickel hydroxide particulate,the addition of ultrasonic energy causes microstructural change to theforming nickel hydroxide crystalline material. The inventors previouslythought that this structural change exhibited itself as disorder in thecrystalline lattice of the nickel hydroxide. The instant inventors alsopreviously theorized that this disorder causes the nickel hydroxide todeposit in a meta-stable beta crystalline lattice, which quicklyconverts to an alpha lattice upon formation and charging of theelectrode and that thereafter the material cycled between the alpha andgamma phases of the material. However, it is now known that the materialactually is formed in an especially useful beta lattice structure(discussed hereinbelow) and that the material cycles between the betaand gamma lattice structures.

Nickel Hydroxide Material Analysis

Analysis of the powders obtained from the ultrasonic precipitationmethod of the instant invention indicate that they have uniqueproperties when compared with industrially available nickel hydroxidematerials and powders made by non-ultrasonic methods. Particularly it isnoted that the powders exhibit the ability to be electrochemicallycycled between the beta and gamma crystalline lattice phases. FIG. 2shows an x-ray plot for nickel hydroxide of the instant invention in thedischarged state showing the predominant beta phase peak at the pointindicated as 4.63337. FIG. 3 shows an x-ray plot for nickel hydroxide ofthe instant invention in the charged state showing the predominant gammaphase peak at the point indicated as 7.09673. Commercially availablenickel hydroxide powder from Tanaka K.K. of Japan typically cyclebetween the beta(II) and beta(III) phases, and powders made bynon-ultrasonic precipitation techniques typically cycle between thealpha and gamma phases.

Another unusual characteristic of the powders of the instant inventionis their unique and unexpected local order. This local ordering ischaracterized by the fact that the OH groups are oriented such that thedistance between OH groups is fixed to a very narrow range by thecrystalline lattice itself.

IR Analysis of Nickel Hydroxide Materials

The IR data was taken using a Perkin Elmer System 2000 Fourier TransformInfrared Spectrometer (FT-IR). FIG. 4 shows three absorption spectra ofdifferent Ni hydroxide powders using the Diffuse Reflectance Accessory.Each sample was diluted in ultra dry finely ground KBr powder (10 wt. %sample: 90 wt. % KBr), and the spectra was obtained by comparing to pureKBr powder (which does not absorb any IR energy). Trace (A) is of anickel hydroxide produced by non-ultrasonic precipitation, trace (B) isof a nickel hydroxide material produced by the ultrasonic method of theinstant invention, while trace (C) is the spectrum of a typicalbeta-Ni(OH)₂ supplied by Tanaka K.K.

The primary spectral region of interest is the wavenumber regioncontaining the O--H stretching band which extends from ˜3700 cm⁻¹ to2500 cm⁻¹. The rich structure of the O--H stretching band indicates thatthere are both different forms of bonded OH and different types of O--Hstretching taking place. The OH group can be bonded to the metal cationas in the Ni(OH)₂ system, or it can be one part of a water molecule. Ineither case, the vibration is primarily the stretching of the bondjoining the O and H atoms. Also, because there are two hydroxyls per Nication, it is possible for the O--H bonds to vibrate eitherasymmetrically or symmetrically relative to one another. The asymmetricO--H stretching band is strongly IR active and is represented by theintense peak near ˜3640 cm⁻¹. The symmetric stretching band should not,strictly speaking, be IR active, but a slight symmetry breaking hasoccurred in the Tanaka sample which allows it to be weakly IR active.This accounts for the relatively weak band at ˜3581 cm⁻¹.

FIG. 4 shows the entire O-H stretching absorption band. There are twoprincipal features that all three traces share: (1) the intense andnarrow band due to the asymmetric O--H stretching vibration (˜3640 cm⁻¹)of the Ni(OH)₂ group; and (2) the very broad band centered at ˜3400cm⁻¹. This broad band is due to the O--H stretching vibration ofH--O--H, i.e., of water groups. The O--H stretching frequency shows anextremely wide range of frequencies, from ˜3700 to ˜2500 cm⁻¹. No otherbonding system shows changes of this magnitude in the vibrationalfrequency. The reason for this involves the effects of hydrogen bonding.The H-bond interaction is essentially an electrostatic interactionbetween the positive charge of the proton on one OH group and thenegative charge of a nearby oxygen atom (which is generally a member ofanother OH group). It is a general rule that as the strength of theH-bond increases, by decreasing the distance between neighboringhydroxyl groups, the O--H stretching vibration decreases. That thefrequency can decrease by over 1000 cm⁻¹ attests to the magnitude of theH-bond interaction of hydroxyls. In fact, only in the HF system is themagnitude of the H-bond interaction stronger than that of the OH system.

It has been stated by various workers studying the beta phase of Ni(OH)₂that the sharp O--H absorption band shows that the OH group is notsubjected to hydrogen bonding. However, a more accurate interpretationis that the narrowness of the band indicates that the OH groups are welloriented where the distance between OH groups is fixed to a very narrowrange by the crystalline lattice itself. It is apparent in FIG. 11 fromthe spectra of traces A and B that their O--H asymmetric stretchingbands at ˜3644 cm⁻¹ are significantly more narrow (2 to 3×) than thecorresponding band (˜3635 cm⁻¹) of the Tanaka sample. Apparently, thesesamples are more ordered on the local scale than the Tanaka sample.

The IR spectra of FIG. 4 shows that the local bonding structures of theultrasonic powders are fundamentally different from the Tanaka powder.In fact, the sample of trace A achieves roughly one electron transfer(which equals the Tanaka powder) even though it has a tremendous amountof bonded water, which the Tanaka sample has very little of. Inaddition, even though the low water concentration in the Tanaka sampleis comparable to the ultrasonic sample of trace B, the electron transferrate for the Tanaka material is fixed at about 1.0, whereas theultrasonic sample of trace B approaches 1.67.

Finally, it should be noted that while beta to gamma nickel hydroxidehas heretofore been known, it has never been cycleable. The instantmaterial has the ability to reversable cycle between the beta and gammaphases. FIG. 5 is a plot of the capacity of "C" size cells utilizing thenickel hydroxide material of the instant invention versus cycle number.As of the time of the filing of the instant application, the cell hascycled 82 times with no loss (and in fact an increase) of capacity. Thenickel hydroxide material, as of the 82nd cycle, has a capacity of 261mAh/g of pasted material. A comparable paste using conventional nickelhydroxide, such as that that available from Tanaka K.K., has a capacityof only about 230 mAh/g.

While the invention has been described with reference to the specificexample set forth hereinabove, the true scope of the invention is not tobe limited by the example.

Specifically, metal ion solution can be a solution of at least one metalsalt selected from the group consisting of borates, nitrates, sulfates,phosphates, carboxylates, fluorides, chlorides, bromides, iodides andmixtures thereof or a solution of at least one organo-metallic compoundselected from the group consisting of beta-diketonates, alkoxides,acetylacetonates, acetates, benzoates, methoxides, isopropoxides andmixtures thereof and the like. In fact, as long as the metal ions aresoluble, they may come from any known salt or metal-organic compound.

Additionally, the metal ion solution can further include at least onechemical modifier metal ion selected from the group consisting of Al, B,Ba, Ca, Ce, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Sr, Y, Zn and mixturesthereof. Preferably the metal ion solution is selected from one of thefollowing groups:

1) nickel ions, cobalt ions and calcium ions;

2) nickel ions, cobalt ions and cerium ions;

3) nickel ions, cobalt ions, calcium ions and magnesium ions; or

4) nickel ions, cobalt ions, and aluminum ions.

Also, the alkali solution may be a metal hydroxide solution, such asNaOH, KOH, LiOH, and mixtures thereof or the alkali solution may be anammonium hydroxide solution.

The alkali and metal solutions may be combine in any order, i.e. thealkali solution may be added to the metal ion solution to effect theprecipitation of nickel hydroxide; the metal solution may be added tothe alkali solution to effect the precipitation of nickel hydroxide oralternatively, the alkali solution and the metal solution may be addedtogether simultaneously to effect the precipitation of nickel hydroxide.

The temperature of precipitation, the mixing rates, the concentrationsof the solutions, the stirring rates, and the power and frequency of theultrasound may all be varied. Specifically at higher ultrasound powers,the density of the nickel hydroxide particulate formed would be higher,thus providing a greater volumetric capacity for the active material.Generally a useful range of frequencies and powers for the ultrasoundenergy would be a power of between about 20-500 watt/cm² and a frequencyof between about 40-2000 kHz.

Therefore, it is to be understood that the disclosure set forth hereinis presented in the form of detailed embodiments described for thepurpose of making a full and complete disclosure of the presentinvention, and that such details are not to be interpreted as limitingthe true scope of this invention as set forth and defined in theappended claims.

We claim:
 1. A nickel hydroxide positive electrode active material, saidnickel hydroxide active material being characterized by:the ability toreversibly cycle between the beta and gamma nickel hydroxide crystallinephases during electrochemical charge and discharge; and being in theform of spherical nickel hydroxide particulate.
 2. The nickel hydroxideactive material of claim 1, wherein said nickel hydroxide materialfurther includes at least one chemical modifier selected from the groupconsisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Sr,Y, Zn, and mixtures thereof.
 3. The nickel hydroxide active material ofclaim 2, wherein said chemical modifier includes cobalt and calcium. 4.The nickel hydroxide active material of claim 2, wherein said chemicalmodifier includes cobalt and cerium.
 5. The nickel hydroxide activematerial of claim 2, wherein said chemical modifier includes cobalt andaluminum.
 6. The nickel hydroxide active material of claim 2, whereinsaid chemical modifier includes cobalt, calcium, and magnesium.
 7. Thenickel hydroxide active material of claim 2, wherein said chemicalmodifier includes cobalt and manganese.
 8. The nickel hydroxide activematerial of claim 2, wherein said chemical modifier includes cobalt andyttrium.
 9. In a pasted nickel hydroxide positive electrode includingnickel hydroxide active material, the improvement comprising:said nickelhydroxide active material being characterized by:the ability toreversibly cycle between the beta and gamma nickel hydroxide crystallinephases during electrochemical charge and discharge; and being in theform of spherical nickel hydroxide particulate.
 10. The nickel hydroxideactive material of claim 9, wherein said nickel hydroxide materialfurther includes at least one chemical modifier selected from the groupconsisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Sr,Y, Zn and mixtures thereof.
 11. The nickel hydroxide active material ofclaim 10, wherein said chemical modifier includes cobalt and calcium.12. The nickel hydroxide active material of claim 10, wherein saidchemical modifier includes cobalt and cerium.
 13. The nickel hydroxideactive material of claim 10, wherein said chemical modifier includescobalt and aluminum.
 14. The nickel hydroxide active material of claim10, wherein said chemical modifier includes cobalt, calcium, andmagnesium.
 15. The nickel hydroxide active material of claim 10, whereinsaid chemical modifier includes cobalt and manganese.
 16. The nickelhydroxide active material of claim 10, wherein said chemical modifierincludes cobalt and yttrium.